The present invention concerns a method of and device for optimizing a machine that cuts material, especially stacked sheets of paper, cardboard, or similar material.
In a known machine for cutting such material the sheets are stacked on a bench and a hydraulic beam descends onto the stack to hold it fast while an adjacent guillotine blade descends perpendicularly to the surface of the bench and cuts through the material. Once the cut has been produced, the blade and the beam are lifted, with the lower edge of the beam following the sharp edge of the blade. Once the sharp edge of the blade is at the same level as the lower edge of the beam, which still rests on the material, the motion of the beam accordingly ensures that the beam will deflect the blade. This prevents the blade from injuring the operator. The beam generally does not rise again until the blade is in an invariable upper position. The beam itself rises into an invariable upper position. The invariable upper positions are slightly higher than the top of any stack of material that might be processed.
There is a drawback to such a machine in that the blade executes unproductive motions when a low stack is processed. Considerable time is lost while the blade descends onto the stack from its upper position and before it can proceed to actually cutting the material. Raising the blade to its upper position once the cut has been produced also takes considerable time. These long intervals considerably decelerate the overall process when the machine is operating automatically. The same drawback, slow processing, can also be ascribed to the time involved in raising and lowering the beam all the way up and down. This is particularly detrimental in that the material cannot be advanced along the surface until the beam is all the way up. The blade's and the beam's unproductive motions can in particularly last longer than it takes to advance a stack of small sheets, labels for example.
German AS 1 190 431 discloses not raising the hydraulically operated beam and blade in a machine that cuts material, especially staked sheets of paper, cardboard, or similar material as unprofitably high as is necessary in a machine that is gear-driven. The material can accordingly be advanced in this embodiment as soon as the blade and beam release the stack.
German AS 1 095 254 discloses switching circuitry for a machine that cuts material, especially stacked sheets of paper, cardboard, or similar material with a blade-accommodating beam and a mechanically controlled automatically operated holdfast beam. The holdfast beam is lifted out of the position in which it holds down the material by a device that actuates the beam's mechanisms and responds to the arrival of the blade-accommodating beam at a specific elevation. The device comprises a switch that includes a roller and a sloping surface that the roller rolls over, controlling the switch. The holdfast pressure is removed when the blade rises above the stack, which is precisely when the holdfast beam begins to rise. The upward motion of the holdfast beam is accordingly dictated by the upward motion of the blade, but the distance traveled by the holdfast beam is not dictated by the height of the stack.
A machine for cutting frozen meat etc. is known from German 2 550 477 B2. The blade operates in conjunction with another blade and is raised and lowered by hydraulic or pneumatic mechanisms. The stroke of the blade can be adjusted to the thickness of the meat to make the operation more economical. A stroke-end switch that can be raised or lowered is positioned in the vicinity of a trigger that travels along with the blade and operates in conjunction with the hydraulic or pneumatic drive. The trigger is actuated either manually or by a device that senses how thick the meat is.